Internship Objective: Assist in mechanical design of EnPower’s 20Ah Li-ion pouch cell design with a complete set of released engineering drawings that have gone through a design review process.
Educational Objective: Gain an industrial and commercial perspective and exposure to Li-ion cell design and manufacturing while solidifying skillsets in computer aided design (CAD), geometric dimensioning and tolerancing (GD&T), and finite element analysis (FEA). Contribute to a rapidly growing startup focused on commercializing the next generation of Li-ion and learn from various members in a high-voltage, high-ampere team.
About EnPower: EnPower, Inc. is a start-up company developing and commercializing advanced lithium-ion (Li-ion) batteries that are capable of extreme fast charging (XFC) and novel energy-to-power ratios. EnPower’s patented multilayer technology enables repeated fast charging of energy-dense electrodes without significant degradation or capacity fade in the batteries, a critical challenge for the mass adoption of electric vehicles. EnPower owns and operates an R&D facility in Phoenix, AZ where it designs, builds, and tests 3.5-7.0 Ah stacked pouch cells. This facility allows EnPower to produce prototype cells for sampling and third-party validation. It also allows the team to work with customers to optimize electrode and cell designs for specific applications.
INTERNSHIP PROJECT DETAILS
Pouch Cell Mechanical Design
Description: EnPower is finalizing its Gen-I unit-cell “stack-level” design that incorporates a multilayer graphite anode and a multilayer NMC811 cathode by January 2022. A “stack-level” design refers to the electrode-separator-electrolyte combinations of a cell that dictate electrochemical performance, which then need to be packaged into a Li-ion cell device—requiring non-trivial mechanical design. EnPower’s preferred cell format is a stacked pouch cell construction, and the company intends to manufacture a 20Ah pouch cell product. The role of the Cell Mechanical Engineer is to develop the mechanical design of the cell based on target dimensions and initial parameters, such as targeted tolerances on electrode coat weights, thicknesses, and presumptive N/P ratios. This includes defining the dimensions of the electrode punches, anode/cathode overhang, separator width, tab welding clearances, drawn pouch cup tolerances, and heat seal locations. The multidisciplinary nature of the role requires the Cell Mechanical Engineer to work closely with the Cell Engineering team responsible for the stack-level design, and ensure electrode thickness tolerances, swell factors, non-uniformities, anticipated swell forces, and required electrolyte amounts are all taken into consideration. Cell designs need to be drawn within SolidWorks, and FEA on swelling, compression, bending, and torsion should be performed. A complete set of released engineering drawings should be produced for each cell design, along with GD&T specifications.
- Familiarize with Li-ion cell manufacturing in general, and understand EnPower’s current and anticipated manufacturing processes and tolerances
- Work with EnPower Cell Engineering team to understand stack-level characteristics, including swell factor, swell force, and electrolyte fill amounts
- Create SolidWorks CAD model of complete cell construction, detailing electrode punch dimensions, separator height, ultrasonic tab welding footprint and clearances, terminal weld positions, pouch cup seating and clearances, and heat seals. GD&T specifications required for all components
- FEA on structural swelling, compression, bending, and torsion on various axes
Deliverables: The following are key deliverables for this Micro-Internship
- D1 – Complete set of released engineering drawings for a 20Ah pouch cell design with GD&T specifications that have gone through a formal design review process, including structural analysis
- D2 – Final presentation to the Engineering Team on design considerations, tolerances, and final output
- D3 – SolidWorks CAD files
We are a small, intimate team that values high integrity, intellectual curiosity, and professional growth while having fun doing it. We hope you enjoy your micro-internship experience, and do not hesitate to ask questions or express opinions!